[R] Getting all possible contingency tables

[David Winsemius]

On Dec 1, 2012, at 7:28 AM, Christofer Bogaso wrote:

> Thanks Bert for your reply.
>
> I am trying to understand/visualize the Sample Chi-Squared  
> Statistic's Null distribution. Therefore I need all possible  
> Contingency tables under Independence case.
>
> What could be better way to visualize that?

In your quest for enlightenment, consider looking at the example in:

?r2dtable

-- 
David.
>
> Thanks and regards,
>
> On 01 December 2012 20:03:00, Bert Gunter wrote:
>> Christopher:
>>
>> Don't do this!
>>
>> If I understand you correctly, you want FIsher's exact test. This is
>> already available in R, using far smarter algorithms then you  
>> would. See:
>>
>> ?fisher.test
>>
>> -- Bert
>>
>> On Sat, Dec 1, 2012 at 5:48 AM, Christofer Bogaso
>> <bogaso.christofer at gmail.com <mailto:bogaso.christofer at gmail.com>>  
>> wrote:
>>
>>    Thanks John for your reply. However still not clear how I should
>>    proceed.
>>
>>    My goal is to generate all possible contingency tables. Basically
>>    I want to see the distribution of Chi-squared Statistic under
>>    independence (NULL).
>>
>>    So I was thinking if I can generate all possible permutation of
>>    integer numbers having sum equal to (8 + 10 + 12 + 6) = 36. Is
>>    there any R function to do that?
>>
>>    Thanks and regards,
>>
>>
>>    On 01-12-2012 18:39, John Kane wrote:
>>
>>        Are you basically asking for all possible permutations of the
>>        table?  If so see ?permn in the combinat package.
>>
>>        John Kane
>>        Kingston ON Canada
>>
>>
>>            -----Original Message-----
>>            From: bogaso.christofer at gmail.com
>>            <mailto:bogaso.christofer at gmail.com>
>>            Sent: Sat, 01 Dec 2012 18:10:15 +0545
>>            To: r-help at r-project.org <mailto:r-help at r-project.org>
>>            Subject: [R] Getting all possible contingency tables
>>
>>            Hello all,
>>
>>            Let say I have 2-way contingency table:
>>
>>            Tab <- matrix(c(8, 10, 12, 6), nr = 2)
>>
>>            and the Chi-squared test could not reject the  
>> independence:
>>
>>              > chisq.test(Tab)
>>
>>                      Pearson's Chi-squared test with Yates'
>>            continuity correction
>>
>>            data:  Tab
>>            X-squared = 1.0125, df = 1, p-value = 0.3143
>>
>>
>>            However I want to get all possible contingency tables
>>            under this
>>            independence scenario (one of them would obviously be the
>>            given table
>>            as, we could not reject the independence), and for each
>>            such table I
>>            want to calculate the Ch-sq statistic.
>>
>>            Can somebody help me how to generate all such tables?
>>
>>            Thanks and regards,
>>
>>

David Winsemius, MD
Alameda, CA, USA